The primary objectives of this planned research are to determine how the structure of the enzyme, galactose-1-PO4 uridyl transferase (gal-1-PUT) as found in the normal population, differs from the nonfunctional form(s) of the enzyme found in those individuals with the inborn error of metabolism galactosemia and to ascertain whether structural differences in the enzyme are the direct cause of deficient catalytic activity. Further studies on the immunochemically determined structural polymorphism of gal-1-PUT in the normal population will be carried out to determine whether these structural differences are genetically- determined and whether they are reflected in divergent electrophoretic mobility of individual enzyme samples. Similar immunochemical and electrophoretic studies will be done on samples from a number of patients with galactosemia and their families. The gal-1-PUT activity as found in certain galactosemic skin fibroblasts grown in tissue-culture will be examined to determine if this activity is the result of tissue-specific isozymes and/or if it is induced by certain characteristics inherent to cell growth in tissue culture. Further studies will attempt to develop an automated immunochemical method for multi-sample determination of variant forms of the gal-1-PUT enzyme in human red blood cells.